Your unhappiness doesn't help anyone else - and in fact, as I mentioned in another answer, happy people are more altruistically inclined. So happiness is not a selfish goal.

When you work regularly, inspiration strikes regularly.

Say “no” only when it really matters. Wear a bright red shirt with bright orange shorts? Sure. Put water in the toy tea set? Okay. Sleep with your head at the foot of the bed? Fine. Samuel Johnson said, “All severity that does not tend to increase good, or prevent evil, is idle."

Act the way you WANT to feel.

In 'Before and After,' I identify the sixteen strategies that we can use to make or break our habits. Some are quite familiar, such as 'Monitoring,' 'Scheduling,' and 'Convenience.' Some took me a lot of effort to identify, such as 'Thinking,' 'Identity,' and 'Clarity.'

Turns out that people who try new things, go new places, learn new skills, etc. are happier. This can be tough, because novelty and challenge also bring frustration and irritation - but if you can push through that, novelty and challenge can bring enormous happiness rewards.

Getting control of stuff makes people feel like they have more control over their lives - maybe irrationally, but it's one of these psychological truths.